The present invention relates generally to medical sensors, and in particular to fiber optic sensors.
Fiber optic sensors, and in particular fiber optic reflectance oximeters, are well known to the art. One example of such a sensor is disclosed in U.S. Pat. No. 4,623,248 issued to Sperinde, which discloses a three wavelength reflectance oximeter. Typically, such sensors are introduced into the vascular system by means of an introducer catheter. Progress of the fiber optic sensor through the introducer catheter can be monitored by means of markings along the fiber optic sensor. However, in order for the markings to be meaningful, it is necessary that the total length of the introducer catheter be known, including al manifolds and fittings through which the sensor must pass. This length can then be compared to the markings on the fiber optic sensor to provide a rough guide as to the position of the distal end of the sensor.
Unless the fiber optic sensor, introducer catheter, and associated fittings and manifolds come as part of a packaged set, it is unlikely that the markings on the fiber optic sensor will line up precisely with the proximal end of the introducer catheter when the tip of the fiber optic sensor is properly positioned relative to the distal end of the introducer catheter. Preferably, the tip of the fiber optic sensor should extend somewhat (a few millimeters) from the end of the introducer catheter, but not an excessive distance.